This application claims the priority of German Application No. 100 52 880.5 filed Oct. 20, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an apparatus and a method for controlling an automatic transmission.
In order to give drivers of motor vehicles with automatic transmissions the opportunity to influence the selected speed increasing ratio directly in special situations, it is known in the art, from xe2x80x9cAutomobiltechnische Zeitschriftxe2x80x9d [Journal of Automotive Engineering], No. 92, Issue 6/1990, pp. 308-319, to envision a manual operation in addition to an automatic operation. In the manual operation, the driver is allowed to select individual speeds of the self-changing gear directly. For this purpose, a second gear-shift channel is envisioned for the manual operation that is parallel to a gear-shift channel for the automatic operation, thus allowing the driver to downshift or upshift in one-gear increments, respectively, by way of the seesaw-like movement of a gear-shift lever. A similar apparatus for infinitely variable change-speed gears is known in the art from CH-Z xe2x80x9cAutomobil Revuexe2x80x9d [Automobile Journal], No. 51/1992, p. 23.
Also known in the art is the possibility of initiating a gear change in a transmission, which is controlled by a separate force, using a selection device on a steering wheel of a motor vehicle (for example, DE-Z xe2x80x9cAuto Motor Sport,xe2x80x9d No. 22/1991, p. 300).
German patent document DE 43 11 886 A1 discloses an apparatus and a method for controlling an automatic transmission. The controller changes from an automatic operating mode to a manual operating mode if, by means of a travel length switch, a position M is lightly tapped, or if, by means of a rocker switch envisioned on the steering wheel, a switch signal is produced for a preset amount of time, e.g. 0.7 seconds. If a position M is lightly tapped once again with the travel length switch, or if for a preset amount of time, e.g. 1.5 seconds, an upshift signal is given, operation in the manual operating mode is discontinued. Finally, it is possible to envision that the driver-influenced operating mode is discontinued if that operating mode was activated over a preset amount of time. In general, however, this process always involves changing over from the automatic to the manual operating mode and vice versa.
German patent document DE 199 12 963 A1 already discloses an apparatus and a method for controlling an automatic transmission having a controller which intermittently changes from the automatic operating mode, that is normally selected in a position D of a travel length switch, without selection by the first selection device, to the driver-influenced operating mode, if a second rocker switch, arranged on the steering wheel is activated. Thus, the automatic operating mode is not discontinued permanently, because, after a preset amount of time has elapsed, the automatic operating mode is reactivated. Every time the rocker switch is activated, the time starts running anew. Returning to the automatic operating mode is only possible if the current transverse acceleration is below a preset limiting value and if traction operation is simultaneously in effect.
It is the subject-matter of the present invention to create an apparatus and a method that provide improved driveability.
According to the invention, this objective is achieved with the characteristics set forth herein. The invention proposes that, subsequent to a brief selection of the second, driver-influenced operating mode, the remaining time before returning to the automatic operating mode be set to a minimum value as soon as one of the referenced conditions, that suppress a return to the automatic operating mode, no longer apply. Thus, advantageously, it is achieved that, after one of the referenced conditions no longer applies, a return to the automatic operating mode does not occur immediately; but a minimum dwell time in the manual operating mode is ensured. The invention thus relies on the realization that the driving states, which cause continued dwelling in the manual operating mode even after the preset time in the manual operating mode has elapsed, can be interrupted for a brief amount of time without simultaneously creating a need to change to the automatic operating mode. Consequently, the overall gear-shift properties of the transmission, in particular the selection of its modes of operation, are therefore improved in terms of their predictability and clarity for the driver. The kinds of referenced conditions that effect a return to the automatic operating mode are not significant in the present context as long as said conditions indicate special driving states. The value for the minimum dwell time should be, preferably, in the range of 25% of the time spent in the manual operating mode.
The method claims share the effects and advantages of the corresponding apparatus claims.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.